This NIH-funded project is a collaboration with investigators at Emory University, Altanta, Georgia, to determine genetic predictors of antihypertensive blood pressure response to thiazide diuretics. A sample of 300 antihypertensive whites from Rochester and a sample of 300 African-American hypertensives from Atlanta will be enrolled in the study. Dr. Stephen Turner of the Mayo Clinic is the PI of the project and is responsible for the overall conduct of the project and is carrying out the study in the non-Hispanic whites in Rochester. Dr. W. Dallas Hall, Program Director of the Emory University GCRC, is a co-investigator on the project and is responsible for carrying out the study protocol in African-Americans in Atlanta. Subjects are studied in the respective GCRCs. The Mayo GCRC grant is supporting laboratory ancillary tests on both studies.